System for Converting Electromagnetic Radiation to Electrical Energy Using Metamaterials

ABSTRACT

Spectral tuning of heat source to emit radiation at a desired frequency or frequency band is accomplished using metamaterials. The metamaterials include a structured geometry having holes with dimensions and spacing chosen such that the resulting surface will emit radiation in the desired spectrum. A collector can be made of a similar metamaterial or antenna array to detect the emitted radiation and transfer it to a converter device that converts the detected radiation to electricity. Embodiments also provide efficient coupling to the converter device for energy harvesting. Cooling of the converter devices can be accomplished using a cooling sink or deep space.

This application is a continuation of U.S. application Ser. No.16/529,976, filed Aug. 2, 2019 (pending), which is continuation of U.S.application Ser. No. 14/745,299, filed Jun. 19, 2015 (now patented asU.S. Pat. No. 10,374,524), which claims the benefit of U.S. ProvisionalApplication No. 62/015,121, filed Jun. 20, 2014 (expired), each of whichis hereby incorporated by reference herein in its entirety.

BACKGROUND Field of the Invention

Embodiments of the present invention relate generally to structures andmethods for harvesting energy from electromagnetic radiation and, morespecifically, to nanostructures, metamaterials and related methods andsystems for harvesting energy from, for example, infrared, near infraredand visible spectrums and capturing millimeter waves and Terahertzenergy.

Background of the Invention

There is a great need for inexpensive renewable energy in the worldright now. Ironically, there is an abundance of energy available in theform of sunlight and heat but using it to support the needs of societyrequires it to be converted into electrical form. Most electrical energyused today comes from a conversion process involving heat. Nuclear,coal, diesel, and natural gas powered electrical generation plants allconvert stored forms of energy into heat for conversion intoelectricity. Processes in these plants are inefficient and often producemore heat as waste than is converted into electricity.

Harvesting sources of heat into usable electrical power is especiallydesirable at low cost. The cost of turbine based solutions is wellestablished at this point. As a result, new technological solutions forconverting heat to electrical power enter a relatively matureenvironment. Because of the need and the fixed pricing environment, newtechnologies are beginning to address this area. These new technologiesinclude thermo photovoltaic (TPV), thermoelectric (TE) and organicrankine cycle (ORC) systems.

TPV technology has encountered difficulties with heat conversionapplications since photovoltaic (PV) converts short wave radiation, notthe long waves found in the infrared (IR) and near IR spectra associatedwith heat. New micron gap methods for bringing such long wave energy tothe PV cell still require conversion technology better suited to thisinflux of long wave radiation. The PV cell band gap favors onlyenergetic photons since lower energy photons do not have the energy tosurmount the gap and end up absorbed, thereby causing heat in the PVcell.

Thermoelectric has only been able to convert heat to electrical power atlow efficiency. To date, TE applications for converting heat toelectricity has been unable to provide substantial efficiencies inenergy conversion. Despite these hurdles, TE has been used in automotivewaste heat recovery, which further demonstrates the need for alternativeheat-to-electric conversion technologies.

Organic Rankine Cycle technology harvests waste heat by chainingturbines together with heat exchangers each with a lower boiling pointliquid in its system. Unfortunately, ORC systems are bulky and havelarge numbers of moving parts. They are also limited to the propertiesof the liquids and ultimately the limit of time, space and marginalresults of additional systems in a working space.

BRIEF SUMMARY OF THE INVENTION

The technology of surfaces of paired nanoantenna and diode arrayspresent tremendous advantages for energy harvesting applications. In thearea of waste heat recovery these systems are ideal since they have nomoving parts, are inexpensive to manufacture and can be tuned to thefrequency spectra of the target source. The ability to tune thecollecting elements of the system to the spectral properties of thesource make these technologies ideal not only for waste heatapplications but for heat harvesting in general and, ultimately, solarenergy harvesting as well.

Embodiments described herein involve a method for tuning to the spectralproperties of a heat source using metamaterial designs. The combinationof collector and source tuning make this a powerful method forharvesting energy from a variety of sources. Beyond tuning of source andcollecting elements, embodiments described herein use methods thatenable thermal energy to be efficiently coupled into nanostructures forenergy harvesting.

In embodiments, a metamaterial device acts as converter betweenpropagating and localized electromagnetic fields, providing an effectiveroute to couple photons into the antenna-based energy harvesters. Thisstructure can exceed the black body radiation limit. The collector arraycomponents of these systems are called Nanoantenna ElectromagneticCollectors (NEC).

Various nanostructure-based metamaterial surface treatments have beendeveloped to enhance energy capture from thermal heat sources.Metamaterial layers tune the thermal emissions of a hot body to radiateenergy in the channels optimized for high efficiency energy conversion.Methods are demonstrated for affordable, large-scale fabrication of thedevice.

Embodiments of the present invention also include systems and methods toharvest electromagnetic radiation from far-field plane waves, to harvestEM radiation from near-field evanescent and/or plasmonic waves, and toharvest electromagnetic radiation using a combination of far- andnear-field effects. Systems and apparatus for energy capture andconcentration include resonant antenna structures and metamaterialfilms. Systems and apparatus for energy conversion include various typesof rectification processes integrated with the antenna device, which isalso referred to herein as a rectenna. Energy conversion apparatus andmethods include, but are not limited to: metal-insulator-metal (MIM),metal-insulator-insulator-metal (MIM), and Traveling Wave Diode (TWD)diode devices.

In an embodiment, the present invention is an energy harvesting systemthat includes resonant elements tuned to frequencies in the range ofavailable radiant energy. Typically, such frequencies are in thefrequency range from approximately 10 THz, in the infrared, to over 1000THz (visible light). In an embodiment, these resonant elements arecomposed of electrically conductive material, and coupled with atransfer element. The transfer element converts stimulated electricalenergy in the resonant element to direct current, to form resonant andtransfer element pairs. In an embodiment, the resonant element andtransfer element pairs are arranged into arrays that are embedded in asubstrate and interconnected to form a power source, for example, for anelectrical circuit or other apparatus or device requiring sourcedelectrical energy to operate. Additional details for resonant andtransfer elements of embodiments are described in U.S. patentapplication Ser. No. 13/708,481, filed Dec. 7, 2012, entitled, “Systemand Method for Converting Electromagnetic Radiation to ElectricalEnergy,” (U.S. Pat. App. Pub. No. US 2013/0146117) (the “'481Application”), U.S. patent application Ser. No. 14/108,138, filed Dec.16, 2013, entitled, “System and Method for Identifying Materials Using aTHz Spectral Fingerprint in a Media with High Water Content” (U.S. Pat.Pub. No. U.S. 2014/0172374) (the “'138 Application”), and U.S. patentapplication Ser. No. 14/187,175, filed Feb. 21, 2014, entitled,“Structures, System and Method for Converting Electromagnetic Radiationto Electrical Energy” (copy attached to U.S. Provisional App. 62/015,121as Appendix A, which is hereby incorporated by reference herein in itsentirety) (the “'175 Application”), each of which is hereby incorporatedby reference herein in its entirety.

In addition to the resonant and transfer elements described above, in anembodiment, the surface of the material is modified to be ametamaterial. The metamaterial enables the surface to radiate energythat matches the spectrum of the NEC components that will harvest it. Inan embodiment, the metamaterial comprises a grid of holes of specificdepth, area, and spacing. These holes produce an artificial surfaceresonance at a specific frequency. This operation is similar to surfaceplasmons on metal surfaces. The electromagnetic field is concentratedover the holes where NEC devices may be placed. Furthermore, the energyavailable for harvesting is most concentrated in the near field, whichis defined as the region within the light wavelength from the surface.In one embodiment, a NEC is placed 3 μm above each hole and the surfaceand NEC are tuned to 1 THz. In another embodiment, a NEC is placed inthe near-field over each hole at less than 0.5 wavelengths of thespecific frequency that causes surface resonance. In embodiments, a NECis placed over some, but not all of the holes. In an embodiment, thespecific dimensions of holes and hole placement are determined bycomputer simulations based on the Maxwell's equations describing theinteraction between light and material. For example, in an embodiment,hole spacing is 50 μm, hole diameter is 10 μm and hole depth is 40 μm.The simulation software used was COMSOL available from COMSOL, Inc. andLumerical, available from Lumerical Solutions, Inc.

In an embodiment, components, elements and substrate of the device arecomposed of metals and materials that allow them to be manufactured inlow cost methods such as roll-to-roll.

In an embodiment, the present invention is a system to convert heat intoelectricity that includes a metamaterial having a surface that is tunedto generate an enhanced electric field at a desired frequency and arectenna placed over the enhanced electric field, at a distance tointeract with the generated electric field, and to produce electricityfrom the generated electric field. In an embodiment, the surface of themetamaterial comprises a plurality of holes with dimensions and spacingto cause the surface to generate the enhanced electric field at thedesired frequency, and wherein a rectenna is placed over each hole. Inanother embodiment, the surface of the metamaterial comprises aplurality of posts with dimensions and spacing to cause the surface togenerate the enhanced electric field at the desired frequency.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a graph of electric field at the surface of a metalsupporting surface plasmon resonance

FIG. 1B is a graph of electric field strength as a function of distanceabove and below the surface in the metal.

FIG. 2 is a graph illustrating the local density of states versusfrequency at different heights above a semi-infinite sample of aluminum.

FIG. 3 is a graph illustrating the emitted energy, at various distancesfrom the surface of a metal, per unit volume per unit frequency across awide spectrum of frequencies.

FIGS. 4A and 4B illustrate the inter-relationship of elements of onemetamaterial structure that generates plasmonic resonance on the surfaceof a metal.

FIGS. 5A and 5B illustrate a cross sectional view of the metamaterialstructure elements.

FIGS. 6A and 6B illustrate a 3-dimensional view of electric fieldstrength simulation results for a rectenna placed near one of the holesin the surface of a metamaterial.

FIG. 7 is a cross sectional view of a metamaterial structure with arectenna placed at the structure aperture.

FIG. 8 illustrates a cross sectional view of a system that can harvestthe earth's heat.

FIG. 9 illustrates a 3-dimensional view of the system of FIG. 8.

FIG. 10 illustrates an embodiment in which THz sources are matched upwith THz sensors to provide electrical output carried via an electricalbus to provide power to an electrical device.

DETAILED DESCRIPTION

The following description is presented to enable one of ordinary skillin the art to make and use the invention and is provided in the contextof a patent application and its requirements. Various modifications tothe described embodiments will be readily apparent to those skilled inthe art and the generic principles herein may be applied to otherembodiments. Thus, the present invention is not intended to be limitedto the embodiments shown but is to be accorded the widest scopeconsistent with the principles and features described herein.

FIG. 1A is a graph of electric field at the surface of a metalsupporting surface plasmon resonance. FIG. 1B is a graph of electricfield strength as a function of distance above and below the surface inthe metal where δ_(d) is the distance above the surface, and δ_(m) isthe distance below the surface. FIG. 2 is a graph showing the localdensity of states versus frequency at different heights above asemi-infinite sample of aluminum. The local density of states representsthe number of available photon states and the larger local density ofstates naturally enables higher optical power density. FIG. 2 shows thelocal density of states is strongly enhanced at the surface plasmonfrequency and this means strongly enhanced optical power density may beachieved at that frequency. The surface plasmon frequency of metal isnot engineerable. It is thus necessary to adopt the metamaterial conceptwhich allows us to design an artificially structured surface whosesurface plasmon frequency can be tuned. FIG. 3 is a graph of the emittedenergy, at various distances from the surface of a metamaterial designedto exhibit surface plasmon modes at 1 THz, per unit volume per unitfrequency across a wide spectrum of frequencies. It shows stronglyenhanced optical energy density at the surface plasmon frequency.

FIGS. 1A, 1B, 2, and 3 demonstrate that a metamaterial can be engineeredto generate an electric field having an enhanced field strength at aresonant frequency that is tunable. As described below, in embodiments,a metamaterial is designed to exhibit resonance, and therefore anenhanced electric field, in the presence of frequencies associated withheat. A rectenna is placed in the electric field to convert the energyin the electric filed to electricity. In an embodiment, a rectenna is adevice having antenna elements responsive to the electric field and atransfer to device such as a MIM or MIIM diode that converts theradiated energy from the antenna elements to electricity.

FIGS. 4A and 4B are schematic diagrams of an exemplary metamaterialstructure at the surface of a hot object 408. Holes 401 are fabricatedin surface 405 using lithographic and etching methods known to thoseskilled in the art. In an embodiment, the size (or area) of holes 401,represented by dimensions 402 (length) and 403 (width), the spacing 406between holes 401, and the depth 407 of holes 401 are determined bysimulation of electromagnetic waves incident on hot surface 405 andelements of structure 408 so that the metamaterial surface supports astrong surface resonance at or near a desired frequency. In embodiments,the desired frequency is 1 THz. An exemplary such surface resonance near1 THz is illustrated in FIGS. 2 and 3. In an embodiment, for example,the simulation numerically solves Maxwell's equations with a givengeometry. FIG. 4B shows an exemplary geometry used for 3-dimensionalsimulations in a particular embodiment. In the embodiment, the hole hassurface dimensions a and b, to represent width and length respectively.Where dimensions a and b are equal, i.e., the hole is square, resonantfrequency can be approximated by:

$\omega_{pl} = \frac{\pi c_{0}}{a\sqrt{ɛ_{H}\mu_{H}}}$

where ω_(pl) is the effective plasmon resonant frequency, c₀ is thespeed of light, a is the size of the holes, ε_(h) is the electricpermittivity and μ_(h) is the magnetic permeability of the material.

Electromagnetic waves such as light exhibit polarization. Various statesof polarization can occur from environmental/material boundaryconditions that induce scatter and absorption. Metamaterials can bedesigned to respond and extract energy from various modes ofpolarization. For example, if dimensions a and b are not equal, i.e.,the hole is rectangular, the metamaterial becomes anisotropic andexhibits difference responses to different polarizations. Similarly inan embodiment, spacing d in the x direction may be different thanspacing d in the y direction. Where spacing d is different in the x andy directions, the metamaterial becomes anisotropic and exhibitsdifference responses to different polarizations.

FIGS. 5A and 5B illustrate an exemplary geometry used for a2-dimensional simulation to determine hole dimensions and hole spacingto achieve a desired resonant frequency according to an embodiment. Inan embodiment, hole spacing and dimension form a periodic structure ofholes 401 in metamaterial 408. As such, the exemplary simulation can besimplified by using a computational cell containing only one unit cellwith a periodic boundary condition. For the direction perpendicular tothe metamaterial surface, an absorbing boundary condition was used tosimulate the infinite extent of the medium. In FIG. 5A, the dimensionsare designated by 402, 403, and 407 for length, width, and depthrespectively, with a hole spacing 406. In FIG. 5B, the dimensions aredesignated as a (area of the hole), d (depth of the hole), and p (holespacing).

In a typical simulation, a plane wave with a fixed wavelength islaunched onto the metamaterial surface and the subsequent reflectedpower is calculated. This simulation is repeated over a range ofwavelengths to obtain a reflectance spectrum. The reflectance spectrumshould exhibit a dip at the wavelength of surface plasmon resonance. Thegeometry (dimensions and spacing of the holes) of metamaterial surfaceis then tuned to shift the resonance dip in the reflectance spectruminto the desired wavelength. Full optimization should also includeminimizing the line width and maximizing the depth of the reflection dipbecause these conditions correspond to the strongest resonance.

In the simulation using the plane wave as described above, the incidentwave must couple to the surface wave in order to produce a dip in thereflectance spectrum. This is achieved by the periodicity of the holeswhich acts as a grating and imparts a momentum necessary for coupling tothe surface wave. Specifically, the grating coupling condition is givenas:

$\beta = {{\frac{2\pi}{\lambda}\sin\;\theta} + \frac{2\pi}{\rho}}$

where λ, θ, and β are the wavelength, incident angle and grating period,respectively. When the propagation constant β matches that of thesurface wave, the incident wave will couple to the surface wave,resulting in a dip in the reflectance spectrum.

While coupling occurs whenever this condition is met, the couplingefficiency may vary. Thus some structures may not show prominentreflectance dips even though surface waves do exist. In order to avoidmissing surface waves due to poor coupling efficiency, dipole sourcesare used in the simulation. Dipole sources are basically harmonicallyoscillating point dipoles. An oscillating point dipole produces anelectromagnetic wave emanating isotropically. By placing many pointdipole sources on the metamaterial surface coupling into the surfacewave is ensured. In this case, the existence of surface wave would bedetected by monitoring the electric and magnetic field patterns near thesurface. A strong enhancement of field intensity near the surfacesignifies the presence of surface wave.

Resonances form on the surface of material 408 at the tuned frequency ofinterest. In an embodiment, this frequency is 1 THz. Materials 408 canbe a variety of materials, including, for example, copper, or any otherhighly conductive material. Other materials may be used if designdimensions are recalculated by simulation as described above. In anembodiment, metamaterial 408 is copper with a thickness of 100 μm.Dimensions for the embodiment are 10 μm for hole length 402, 10 μm forhole width 403, 50 μm for hole spacing 406 and 40 μm for hole depth 407.

FIGS. 6A and 6B illustrate schematically a rectenna 601 placed over ahole 401 with field intensity mapping. Rectenna 601 comprises antennaelements 601 a and 601 b, and a diode 602. Placing rectenna over a hole401 in the surface of a metamaterial as shown in FIGS. 6A and 6B is todeliver a concentrated electric field to antenna elements 601 andthereby to diode 602, where harvesting of radiant energy to electricityoccurs. Once radiant heat energy is harvested it is carried to a busstructure via leads 603 and 604, and can be used to power electronicdevices or to electricity storage facilities. Additional details forrectenna 601 are described in the '481 Application, the '138 Applicationand the '175 Application.

FIG. 7 illustrates a cross sectional view of a metamaterial 408 with arectenna 601 that comprises antenna elements 601 a and 601 b and a diode602. In the embodiment shown in FIG. 7, hole 401 is filled with a highlyinsulating material 708. Exemplary highly insulating materials 708include SUB, Aerogel, air, and vacuum. Material 708 must be insulatingbut transparent to radiation. Rectenna 601 is set at a distance 703 fromthe surface of the metamaterial 408. This distance is important sincethe power of the electric field decreases exponentially with distancefrom the surface. In one embodiment the distance is at or approximately3 μm which offers a good balance of thermal insulation and proximity forfield strength. In another embodiment, rectenna 601 is placed in thenear-field over hole 401 at less than 0.5 wavelengths of the specificfrequency that causes surface resonance. In an embodiment with aplurality of holes 401, a rectenna 601 is placed over each hole 401. Inan embodiment with a plurality of holes 401, a rectenna is placed oversome, but not all, holes 401.

Materials 706 and 707, on top of rectenna 601, conduct heat and couplethe rectenna 601 to a cold source 710. Materials 704 and 705, whichsurround rectenna 601, are insulating to prevent lost heat from thesource 701 and serve to guide heat via radiation to rectenna 601.

FIG. 8 illustrated an embodiment of the present invention that isconfigured to harvest heat from the Earth in the context of the lowtemperature of deep space. In such embodiment, deep space acts as thecooling source for a rectenna 1101. As shown in FIG. 8, rectenna 1101 isplaced in the near field of post metamaterial structure 1104. Poststructure 1104 concentrates the electric field, generated by a surfacefrom heat delivered by a terrestrial source (e.g., Earth), and deliversthis electric field at a frequency set by the design of the surfacemetamaterial structures using a simulation as described above. Tomaximize the Carnot system advantages of this system it is desirable totune rectenna 1101 to a frequency in a clear band of the Earth'satmosphere. Two such bands are well known: 3 μm to 5 μm and 8 μm to 12μm. Rectennas tuned in this band will radiate freely with the coldsource of deep space and create a system whose Carnot zone is nearly100% (C=1−Tc/Th; where Tc=3K and Th=300K).

In an embodiment using deep space as a cold source, as shown in FIG. 8,the metamaterial is in the form of a plurality of posts 1104, ratherthan holes 401, one of which is shown in FIG. 8. In an embodiment, aplurality of posts are placed periodically as described above for holes401. Post 1104 is surrounded by a heat insulating and radiationtransparent material 1103. An exemplary such material 1103 is Aerogel.In another embodiment, material 1103 is replaced with a vacuum tooptimize thermal insulation properties. In an embodiment, rectenna 1101is placed at or approximately 2 μm above post 1104. In anotherembodiment, a rectenna 1101 is placed in the near-field over post 1104at less than 0.5 wavelengths of the specific frequency that causessurface resonance. In an embodiment, a rectenna 1101 is placed over somebut not all posts 1104. In an embodiment, post 1104 is at least theheight of ¼ wavelength of the tuned frequency of rectenna 1101. Postdesign 1104 allows an element of rectenna 1101 to radiate into space1106 since it is more than a quarter wavelength away from the surface ofthe metal. The combination of near proximity to post 1104 and greaterthan quarter wavelength to the surface metal 1105 allows rectenna 1101to receive energy from the tuned metamaterial 1104 yet still radiateinto deep space 1106.

It is advantageous for the tuned frequency of rectenna 1101 to equal thetuned frequency of the metamaterial 1104 so surface plasmons willdeliver energy most efficiently to the rectennas 1101. Also, rectennas1101 need to be tuned within the clear band regions of the atmosphere.

The system illustrated in FIG. 8 harvests energy as electricity sincerectenna 1101 is stimulated into oscillation by terrestrial heat. Asource of efficiency in embodiments results from the reflection ofenergy coming from nearby terrestrial sources that is in the bandsoutside the clear atmospheric windows. The system needs to reflect awaythis “out of band” energy for rectenna 1101 to stay cooled by deep space1106.

This is part of the purpose of environmental overcoat 1102.Environmental overcoat 1102 is heat insulating and radiation transparentin the “in band” wavelengths of the atmosphere, i.e., in the clear band.Directionality is also an important factor in design. Because the systemis in contact with the sky, rectennas 1101 need to be pointed toward thesky and not obscured by intervening objects.

FIG. 9 illustrates a plurality of such elements. Metamaterial posts 1104on surface 1105 create the plasmonic structure that concentrates aplasmonic electric field at the tips of the post structures. Rectennas1101 are placed in the near field of this structure and tuned for nearfield resonance at the plasmonic frequency. The tuning of rectenna 1101must also match a portion of the transparent window in the atmosphere.

If an antenna is substituted for rectenna 1101 in the embodimentillustrated in FIGS. 8 and 9, the system converts heat energy toradiation at the tuned frequency of the antenna. Such a system hassignificant advantages for use as an inexpensive source of THzradiation. In particular, surfaces covered with THz tuned antennas(matched to tuned metamaterial 1104) generate THz radiation at very lowcost. The entire THz range can be generated by covering a surface 1105with subregions of the surface tuned to subregions of the THz spectrum(both antennas and metamaterials).

FIG. 10 illustrates a system for generating THz radiation according toan embodiment. THz sources layers 1202 are matched up with THz sensors1204. THz source layers 1202 and THz sensors 1204 can be as thosedescribed in the '481 Application, the '138 Application and the '175Application.

As illustrated in FIG. 10, a heat source 1201 generates heat. A THzsource layer 1202 comprises a THz metamaterial and an antenna tuned toTHz frequencies. In response to the heat generated by heat source 1201,the metamaterial in THz source layer 1202 generates energy at the tunedTHz frequencies. The antenna devices in THz source layer 1202, which arealso tuned to the THZ frequencies, radiate THz radiation to THzdetectors 1204. THz detectors 1204 respond to the radiated THz radiationto provide electrical output carried via electrical bus 1205 to providepower to an electrical device, for example, a computer 1206, which caninclude, among other things, for example, digital processingcapabilities, storage, and display. In an embodiment, THz sources 1202are such as described above with respect to the antenna variationdescribed above with respect to FIGS. 8 and 9. This system providesactive illuminated THz detection at low cost at standoff distances. Boththe THz sources 1202 and detectors 1204 are tunable within the THz rangeso such a system is highly flexible and deployable to a variety ofapplications.

What is claimed is:
 1. A system for harvesting electricity fromelectromagnetic radiation, comprising: a metamaterial that is heated bya heat source and has a surface that is engineered to exhibit resonancethat generates an electric field having an enhanced electric fieldstrength in the presence of frequencies associated with heat; and arectenna having an antenna element and a transfer structure, wherein therectenna is placed in the enhanced electric field generated over themetamaterial surface and converts energy in the electric field toelectricity.
 2. The system recited in claim 1, wherein the surface ofthe metamaterial has a plurality of holes over each of which an electricfield is concentrated when the metamaterial is heated and wherein arectenna is placed in the electric field concentrated over one or moreof the holes.
 3. The system recited in claim 2, wherein the rectenna areplaced with 3 μm over one or more of the plurality of holes.
 4. Thesystem recited in claim 2, wherein the rectenna are placed within onehalf the tuned frequency wavelength over one or more of the plurality ofholes.
 5. The system recited in claim 2, wherein each hole is squarewith a side length of a, and the tuned frequency ω_(pl), is determinedas: $\omega_{pl} = \frac{\pi c_{0}}{a\sqrt{ɛ_{H}\mu_{H}}}$
 6. The systemrecited in claim 2, wherein each hole is circular has a depth ofapproximately 40 μm, the spacing between holes is approximately 50 μm,and each hole has a diameter of approximately 10 μm.
 7. The systemrecited in claim 2, wherein each hole is square has a depth ofapproximately 40 μm, the spacing between holes is approximately 50 μm,and each side has a length of approximately 10 μm.
 8. The system recitedin claim 2, wherein the distribution of plurality of holes is periodic.9. The system recited in claim 1, wherein the rectenna are configured tobe tuned to 1 THz.
 10. The system recited in claim 1, wherein themetamaterial surface is engineered to exhibit a dip in a reflectancespectrum at a frequency associated with heat.
 11. The system recited inclaim 12, wherein the dip in the reflectance spectrum has a minimizedwidth and a maximised depth.
 12. The system recited in claim 1, whereinthe components of the system are configured to be manufactured usingroll-to-roll technology.
 13. The system recited in claim 1, wherein themetamaterial is copper.
 14. The system recited in claim 1, wherein themetamaterial has a thickness of 50 μm.
 15. The system recited in claim2, wherein each hole is filled with a highly insulating material that istransparent to radiation.
 16. The system recited in claim 1, whereinmaterials on top of the rectenna couple the rectenna to a cold source.17. The system recited in claim 2, wherein each hole is filled with ahighly insulating material that is transparent to radiation.
 18. Thesystem recited in claim 1, wherein the rectenna is surrounded by aninsulating material to prevent lost heat from the heat source, and toserve to guide heat via radiation to the rectenna.
 19. The systemrecited in claim 1, further comprising materials on top of the rectennato conduct heat and couple the rectenna to a cold source,